MONT VENTOUX, France — British rider Chris Froome showed why he remains the overwhelming Tour de France favorite by winning Sunday’s grueling 15th stage up to Mont Ventoux to extend his lead over main rival Alberto Contador.

Froome attacked about two-thirds of the way up the mammoth 13-mile Ventoux, and his acceleration was too much for two-time former champion Contador. The Spaniard dropped back to sixth and finished about 1 minute, 40 seconds behind as tens of thousands of people crammed the roadside on Bastille Day — France’s National Day.

“This is massive. Everyone wanted to win this stage today, on Bastille Day, being on top of Mont Ventoux,” Froome said. “It really was an epic stage today.”

The win means Froome effectively made up the time he lost on Friday’s sprint stage, when Contador caught him with a surprise attack. He leads Dutchman Bauke Mollema by 4 minutes, 14 seconds and Contador by 4:25.

“It wasn’t really about sending (Contador) a message, but I’m obviously going to take as much time as I can,” Froome said. “I’m really happy to have this advantage now.”

“My objective today was to take a bit of time in the general classification, but I didn’t think I could win the stage,” Froome said. “I thought Quintana would win it. But his legs started to go in the last two kilometers.”

The longest stage of the race took riders over 151 miles from Givors in the winemaking Rhone Valley and ended in the Provence region.

Ventoux is one of the most famed climbs in the Tour’s 110-year history. Britain’s Tom Simpson collapsed and died on it during the 1967 Tour.

Froome raised his right arm in the air when he crossed the line for his second stage win of the race after winning a mountain stage in the Pyrenees on Stage 8 with a similarly decimating attack.

“It was incredible today, incredible. This is the biggest victory of my career,” Froome said. “I didn’t imagine this, this climb is so historical. It means so much to this race, especially being the 100th edition.”

Froome said he needed “five or 10 minutes on the oxygen” mask after the stage.

Froome’s Sky team manager Dave Brailsford hailed his rider as “above his competitors,” adding that “every time it’s been man against man, Chris has shown he’s up to the challenge.”

It is the first Tour since Lance Armstrong was stripped of his seven Tour titles (1999-2005) for serial doping.

Froome has twice been asked during the race if he is racing clean and answered in the affirmative.

He was not asked after Sunday’s stage, but Brailsford said “we have a great performance and 10 minutes later I jump for joy like this, and then 10 minutes later I guarantee you I’ll be answering all these questions and allegations about doping for the next few days.”

A nine-man breakaway group, including sprint champion Peter Sagan and French veteran Sylvain Chavanel, led early in the race. Sagan picked up more valuable points in his quest to win the green jersey for the second straight year, extending his already massive lead over Brit Mark Cavendish, the 2011 Tour sprint champion.

Reputed to be one of cycling’s showmen, Sagan lifted his front wheel and did a wheelie, followed by a salute to the crowd in a rare moment of frivolity on an otherwise difficult day.

The small group of front-runners split open on Ventoux, leaving Chavanel alone in front, and with about 9 miles of climbing still to go. Froome, meanwhile, only had two Sky teammates — Australian Richie Porte and Britain’s Peter Kennaugh — to help him.

Andy Schleck, the 2010 Tour champion, was dropped straight away while the 36-year-old Cadel Evans, who won the 2011 Tour, also faded, as did Chavenel.

With about 6 miles to go, Contador still had three teammates with him but Froome would lose them all.

Other countries were well represented. There were dozens of Union Jacks and Norwegians and Danes wearing Viking costumes. Pockets of Belgians and Dutch swigged beers, others dressed up as animals or ran alongside the riders in inflatable body suits.

The chaotic, raucous, deafeningly loud scene included motorbikes and spectators perilously close to the riders. Toward the top it was windy, overcast and cool, a welcome respite from the stifling heat below, with temperatures again well into the 90s.

Following a rest day Monday, there is a medium mountain stage on Tuesday — 104 miles from the medieval cliff-top town of Vaison-la-Romaine in Provence to Gap in the Alps.

Then come the final few days of agony in the mountains.

There are three straight days of tortuous climbing — including two ascents up the famed l’Alpe d’Huez pass in one day on Stage 18. The next two days both feature two Hors Categorie climbs each — so tough they are considered beyond classification.